Automated perimetry to detect visual field loss in glaucoma has become available to most researchers and clinicians in the past decade. Several analytic methods for identifying patients with visual field defects on automated perimetry have been developed and tested during this time. However, methods for identifying whether field defects progress over time have not been well tested since longitudinal visual field data of sufficient follow-up and sample size are only now becoming available. The National Eye Institute currently sponsors three randomized clinical trials to compare different treatments for glaucoma patients. These are the Advanced Glaucoma Intervention Study (AGIS) , Collaborative Initial Glaucoma Treatment Study (CIGTS) and the Early Manifest Glaucoma Trial (EMGT) trials. Each study has developed a different protocol for determining progressive visual field loss. Two trials use a system of grading and scoring fields. The scores are to be used to identify patients whose visual field worsens during the study. The third uses the Glaucoma Change Probability maps of the Humphrey Statpac program. However, the three different methods proposed by the studies have not been evaluated by applying them to a large longitudinal data set with extensive follow-up. We propose to evaluate and compare the three different approaches to the assessment of visual field progression using two different longitudinal data sets of patients not involved in these clinical trials. This will allow for the identification of similarities and differences between the three approaches using the same data sets.